This invention relates to a ground drilling or cutting tool, and to an attachment means for attaching cutting elements to ground drilling or cutting tools.
Some ground drilling or cutting tools comprise one or more cutting elements and it is desirable for those cutting elements to be replaceable. This enables damaged cutting elements to be replaced or worn cutting elements to be removed for re-work.
The working conditions for drilling equipment are exceedingly arduous and it is very difficult to construct drilling equipment so that the cutting elements are removable. The most reliable and easiest way of attaching cutting elements to a cutting tool is to fix them in place by welding.
For example, a cutting element may comprise a roller cone which is rotatably secured to an arm, where the arm is in turn welded to the body of the drilling or cutting tool. A number of such cutting elements may be spaced around the periphery of the drilling or cutting tool.
Welding of the cutting elements to the cutting or drilling tool presents some difficulty in maintaining the cutting element though. Massive rotary drilling tools can each have a large number of cutting elements that will each require, on a periodic basis, to be re-worked or replaced. Obviously, in the case of a welded cutting element, the re-working must occur with the cutting element in situ. Given that some drilling and cutting tools may be quite large, such an operation becomes quite a task.
In addition, when the cutting elements finally become unserviceable, then it is more likely for the drilling or cutting tool to be discarded in its entirety rather than attempting to rework the tool by removing cutting elements.
Cutting tools and elements of the above described type are well known to the applicant. The applicant's previous attempts to overcome at least some of the problems associated with the above described cutting tools and elements is disclosed in their earlier filed PCT application WO/2004/065752, also entitled ATTACHMENT MEANS FOR DRILLING EQUIPMENT, the content of which should be considered included herein by way of reference. This earlier application discloses an attachment means wherein there is a first surface on the cutting element, a second surface on the tool upon which the first surface locates, dowel holes in each of the first and second surfaces, dowels that locate in aligned dowel holes between said surfaces. Also provided are engagement surfaces on the cutting element and tool that extend substantially parallel to the longitudinal axis of the tool and engage to resist side loads applied to the cutting elements and fastening means that secures the cutting elements to the tool. This arrangement provides a means of easily removing the cutting elements from the tool for either replacement or maintenance work.
It is an object of the present invention therefore to provide a ground drilling or cutting tool having improved (at least when compared with the disclosure of the applicant's above mentioned earlier filed patent application) cutting tool retention, or at least provide an attachment means that is a useful alternative to known attachment means.
Other objects and advantages of the present invention will become apparent from the following description, taking in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.